Magic Number Pt-13 and Misshapen Pt-12 Clusters: Which One is the Better Catalyst?

作者：Imaoka Takane; Kitazawa Hirokazu; Chun Wang Jae; Omura Saori; Albrecht Ken; Yamamoto Kimihisa^*

来源：Journal of the American Chemical Society, 2013, 135(35): 13089-13095.

DOI：10.1021/ja405922m

A relationship between the size of metal particles and their catalytic activity has been established over a nanometer scale (2-10 nm). However, application on a subnanometer scale (0.5-2 nm) is difficult, a possible reason being that the activity no longer relies on the size but rather the geometric structure as a cluster (or superatomic) compound. We now report that the catalytic activity for the oxygen reduction reaction (ORR) significantly increased when only one atom was removed from a magic number cluster composed of 13-platinum atoms (Pt-13). The synthesis with an atomic-level precision was successfully achieved by using a dendrimer ligand as the macromolecular template strictly defining the number of metal atoms. It was quite surprising that the Pt-12 cluster exhibited more than 2-fold catalytic activity compared with that of the Pt-13 cluster. ESI-TOF-mass and EXAFS analyses provided information about the structures. These analyses suggested that the Pt-12 has a deformed coordination, while the Pt-13 has a well-known icosahedral atomic coordination as part of the stable cluster series. Theoretical analyses based on density functional theory (DFT) also supported this idea. The present results suggest potential activity of the metastable clusters although they have been %26quot;missing%26quot; species in conventional statistical synthesis.

• 出版日期2013-9-4